1. Field of the Invention.
This invention has relation to revolver cranes, and more particularly to a crane having a ground supported ring in concentric relation to an upper machinery platform which is rotatably mounted, through a bull gear roller path, on a traction module supported carbody. A boom foot carrier and a counterweight carrier are pivotably mounted to forward and rearward portions of the platform, respectively. A boom and mast are pivotably mounted to the boom foot carrier to be supported for movement along the ring, and a trailing counterweight is supported by the counterweight carrier for movement along the ring.
A conventional crane has a carbody supported on a pair of spaced-apart crawlers, for example, and has a machinery platform which is mounted, through a turntable bearing or bull gear roller path, for rotation on the carbody. A boom is pivotably connected to a forward end of the machinery platform, and a counterweight is secured to the rearward end of the platform. In this configuration, the weight of the load, and the weight of the counterweight, must be transmitted to the carbody (and the ground) through the turntable bearing. Consequently, the load which can be lifted by the crane is limited to a load which can be supported by the machinery platform without damage to the turntable bearing, and/or without exceeding a safe margin on overturning.
2. Description of the Prior Art.
Many efforts have been made in the past to transfer the load carried by the boom, and/or the weight of the counterweight, around (instead of through) the turntable bearing or roller path. See U.S. Pat. No. 4,196,816 to Dvorsky et al, granted in April of 1980.
See also German Pat. No. 1,185,353 to Hans Scheuerpflug, published Jan. 14, 1965. This German Scheuerpflug patent shows a boom foot carrier or intermediate member 2 pivotably mounted to a machinery deck or upper carriage 1 and supported by lateral support rollers 3 on a live support ring 4 which is carried by support plates 5-8 resting on bolsters which are in contact with the ground surface. A jib or boom 10 and a support mast 11 are pivoted on the boom foot carrier 2 so that the vertical components of forces acting on the boom and mast are transmitted directly to the ground. A counterweight 12/13 is supported on a forked lever 14 which extends up the entire length of the machinery deck to be pivoted underneath the boom foot carrier. The forked counterweight support lever 14 is supported at an intermediate fulcrum point by two rollers 16 which are themselves rolling on a separate internal live ring 17 or, in another form of the invention, can roll on and be supported by the same live support ring 4 as is the front end of the boom foot carrier 2.
The patent to Holt, U.S. Pat. No. 1,159,841 granted in November of 1915, shows a machinery platform (or swing frame) rotatably mounted on a carbody (or main frame). The boom is mounted at one end of the machinery platform, and a heavier prime mover (which acts to counterbalance the load) is mounted at the other end of the platform. A pair of slide blocks are mounted under the prime mover, between the machinery platform and the carbody to partially support the load imposed on the machinery platform and transfer that load to the carbody.
The U.S. patent to Scheuerpflug, U.S. Pat. No. 2,910,189, granted in October of 1959, shows a machinery platform mounted for rotation on a carbody. A boom is pivotably mounted at the outermost forward end of the boom foot carrier which, in turn, is pivotably connected at its innermost end to the machinery platform. The boom foot carrier rolls on a support ring which is supported on the ground to transmit the load of the boom directly to the support ring and from the support ring directly vertically to the ground.
The patent to Beduhn, U. S. Pat. No. 3,485,383, granted in December of 1969, shows a crane with a machinery deck mounted for rotation on a carbody. An auxiliary support ring mounted on the ground surrounds the carbody, and supports the outermost end of a boom foot carrier which is pivotably connected at its innermost end to the machinery platform. A boom is mounted at the outermost end of the boom foot carrier directly over the ring to transfer the load of the boom through the support ring to the ground. The machine has two counterweights, one permanently mounted on the machinery platform and one slidably mounted on the machinery platform but supported by the support ring.
The aforesaid patent to Dvorsky et al shows a machinery platform (or upper works) rotatably mounted on a carbody (or lower works). A support ring surrounds the carbody and is connected to it. A rigid rectangular auxiliary frame is mounted on the support ring, surrounding the machinery deck, for rotation on the ring in unison with rotation of the machinery deck. A mast (or gantry) and a boom are pivotably mounted to the auxiliary frame to have position directly over the rollers supporting the frame on the support ring. A counterweight is mounted to the auxiliary frame opposite the mast and boom to be supported directly over rollers supporting the auxiliary frame on the support ring.
The patent to Brown et al, U.S. Pat. No. 3,842,984, granted in October of 1974, shows a crane having a machinery platform which is mounted, through a bull gear roller path, for rotation on the carbody. A mast and a boom are pivotably connected directly to the machinery platform to rotate with the machinery platform on wheel assemblies supported directly on the ground. A machinery platform counterweight is mounted on the rear of the machinery platform.
All of the foregoing serve in one manner or another and to at least some degree to transfer some of the weight of the boom and/or counterweight around (instead of through) the turntable bearing or roller path. However, another important consideration is the minimizing of the ground pressure loading directly under the support ring. The weight of the auxiliary or trailing or supplemental counterweight riding on a ring is a known factor and, therefore, the stresses on the structure under the support ring in alignment with the trailing counterweight can be calculated and the structures can be such that a maximum desired loading of the ground under the trailing counterweight is not exceeded. It would be helpful, however, when the boom is handling its maximum load, if all of this loading was not taken by the support ring and the structure under it and some of it could be transferred back to the machinery platform and even through the turntable bearing or roller path to the carbody.
In the patent to Brown, et al, virtually all of the weight of the trailing counterweight is used to counterbalance the load, and only when most of the weight of the trailing counterweight is utilized does the machinery platform supported counterweight begin to counteract major additional increments of loading. A similar situation appears to exist in connection with the Beduhn patent. A prior art structure is not known in which the trailing counterweight and the machinery platform mounted counterweight each assume part of the counterbalancing of the boom supported load in predetermined equal proportion.
The inventors and those in privity with them are aware of no closer prior art than that set out above, and they are aware of no prior art which anticipates the claims herein.